Solenoid



Oct. 6, 1964 P. TRoMBx-:TTA 3,152,239

SOLENOID Filed Feb. 14, 1961 2 Sheets-Sheet l Oct. 6, 1964 P. TROMBETTA 3,15%?89V SOLENOID Filed Feb. 14. 1961 2 Sheets-Sheet 2 lll |44 ISBD w32 lm IN VEN TOR. PANFILO TROMBETTA gmumh United States Patent() "ice 3,152,289 SOLENOID Pantlo Trombetta, 329 N. Milwaukee St., Milwaukee, Wiso Filed Feb. 14, 1961;, Ser. No. 89,191 6 Claims. (Cl. 317-191) The present invention relates to electric solenoids and more particularly to electric solenoids especially adaptable for operating electromagnetically controlled devices such as industrial brakes and the like.

In some arrangements of industrial brakes and the like it is desirable to employ an electromagnet which, when energized, is effective to push against the brake setting arm. In other arrangements it is desirable to provide an electromagnetic solenoid which exerts a pull on the brake setting arm. An electromagnetic solenoid, of course, is constructed so as to provide pull on the plunger in one direction only; that is, if the load is attached to one end of the plunger, the solenoid is said to be of the pull type, but if the load is attached to the other end of the plunger by means of bars extending through the end plate of the solenoid frame it is said to be of the push type. It is, of course, desirable that the same solenoid construction be applicable to push type and to pull type applications in order to minimize the number of different types and sizes of solenoids which must be manufactured and stocked.

The push type plunger has to have one or more pusher bars that will project from one end of the solenoid frame in order to push the load when the plunger is attracted to the frame in the closed circuit or energized position of the solenoid. It is necessary that these pusher bars be of nonmagnetic material, such as brass or stainless steel, where they extend beyond the plunger otherwise the magnetism in the frame is shunted away from the plunger through the pusher bar extensions. Moreover, the bars must be ystrong enough to sustain the load that the solenoid has to take, and also withstand the shocks incidental to the operation of a solenoid. On the other hand, it is undesirable that the pusher bars of nonmagnetic material be extended the entire length of the plunger since, in some cases, the total cross-sectional area of the pusher bars may reach as much as 20% of the total crosssectional area of the plunger and the eiective thickness of the plunger is diminished by the area.

In the design of commercial solenoids, it is necessary to saturate the plunger with magnetic flux to the maximum value in order to obtain the maximum pull from the amount of material used. When the frame ofa sole noid is made to admit the plunger of a particular size, the solenoid will have a certain amount of pulLWhich is limited by the size of the solenoid, by the heating of the winding and the magnetic density in the plunger, which determines the hysteresis and the eddy current losses as well as the copper losses because the magnetizing current is a function of the flux density of the iron circuit. It the solenoid were to be converted from a pull type to a push type solenoid and if the pusher bars were made of nonmagnetic material then the thickness of the plunger would be diminished by the combined thickness of the pusher bars. The effective cross-section of the plunger in the push type solenoid will then be reduced from that of the pull type solenoidso that a larger size ksolenoid would be required for the push operation than for the pull operation. More importantly, however, is the fact that a solenoid of a given size would not have the same capacity both in the pull and the push types.

Particular dimculty has been experienced in the adaptation of solenoids to push type operation when they are of laminated construction, such as would be used with alternating current. Such difticulty has not been as pro- 3,152,289 Patented Oct. 6, 1964 nounced in pure direct current solenoids where a solid plunger may be used since it is possible to thread a pusher rod into a direct current plunger because the plunger is solid; but to attach one or two pusher bars to a laminated plunger is not very easy, and the most convenient way of doing this is by riveting two bars, one on each side of theplunger, or one bar in the middle of the plunger to the laminations of the plunger. As described above, the portion of these bars that comes out of the solenoid through the frame should be nonmagnetic. Moreover, the bars have to be strong enough to sustain the load that the solenoid has to carry and also to withstand the shock incidental to the operation of a solenoid. It is, of course, possible to construct a solenoid of a given size which will have the same capacity in both the push and the pull types with nonmagnetic pusher bars which reducer the pulling capacity of the solenoid; but it is desirable to elevate the capacity of the push type solenoids to that of the pull type solenoids in order best to fully utilize the magnetic material.

Accordingly, it is an object of the present invention to provide a new and improved electromagnetic solenoid.

It is a further object of the present invention to provide an improved electromagnetic solenoid of the type which may be used as a push type or as a pull type solenoid.

Still another object of the present invention is the provision of an electromagnetic solenoid of the laminated type which develops substantially the same pulling force when used either as a pull type solenoid or a push type solenoid.

Still another object of the present invention resides in the provision of an improved electromagnetically con trolled industrial brake.

Further objects and advantages of the present invention will become apparent as the following description proceeds and the features of noveltywhich characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification. f

For a better understanding of the present invention reference may be had to the accompanying drawings in which:

FIG. l is an elevational view of one embodiment of the present invention showing a spring-set electromagnetically released type of industrial brake;

FIG. 2 is an elevational View, partly in section, of the improved solenoid of the brake of FIG. 1 and illustrating the plunger assembly in its de-energized position;

FIG. 3 is a side elevational sectional viewkof the solenoid of FIG. 2 taken along line 3 3 of FIG. 2, assuming that FIG. 2 shows the complete solenoid and illustrating the plunger assembly in its energized position;

FIG. 4 is a front elevational View, partly in section, of

kanother embodiment of an improved solenoid according o to the present invention, and illustrated in a de-energized ,noid according tothe present invention, shown in a deenergized position;

FIG. 7 is a side sectional view of the improved solenoid of FIG. 6, taken along line 7 7 of FIG. 6, and assuming that FIG. 6 shows the entire solenoid; and

FIG. 8 is a partial bottom sectional view of the improved solenoid of FIGS. 6 and 7, takenalong line 8 8 of FIG. 7, and assuming that FIG. 7 illustrates the whole solenoid. i

Briefly, the present invention is concerned with an improved electromagnetic solenoid which, for a given size, has the same capacity both in the pull and the push type solenoids. According to the present invention, this is accomplished by providing a plunger assembly having an operating portion of magnetically attractive material and provided with pusher bars having a plunger portion of magnetically attractive material secured to the operating portion and having a nonmagnetic pusher portion. The plunger portion of the pusher bar and the operating portion together form the magnetic path of the plunger assembly so that the effective cross-sectional area of the magnetic path of the plunger assembly is substantially the same for both a pull type and a push type solenoid; on the other hand, the portion of the pusher bar extending beyond the operating portion of the plunger assembly is formed of nonmagnetically attractive material so that the magnetic flux is not shunted away from the solenoid frame through the pusher portion. This results in what is hereinafter referred to as amputated pusher bars wherein the pulling capacity and the pushing capacity of the solenoid is the same.

Referring now to the drawings and specifically to FIG. 1 thereof, there is illustrated an improved push type solenoid 12 according to the present invention and shown. operatively connected in a spring-set, electromagneticallyreleased industrial brake unit, generally indicated by the reference numeral 10. As illustrated, this industrial brake 1@ comprises a conventional brake drum or brake wheel generally indicated as 14 and secured to a shaft 16 of a suitable device which might be a prime mover, such as an electric motor or the like. For the purpose of frictionally controlling the brake drum or wheel 14, there is provided a pair of brake shoes 18 and 20 which have the conventional concave surfaces conforming to the shape of the periphery of the brake drum 14 and each provided with a conventional brake lining 22. In order to support the brake'shoes 18 and 20 adjacent the brake drum 14, there is provided a pair of brake shoe supporting arms 24 and 26; the lower portions of these shoe arms are pivotally mounted to a base member 2S through a pair of pivot pins 30 and 32, respectively.

For the purpose of causing relative movement between the shoe supporting arms 24 and 26, there is provided a main lever 38 having one end 38a pivotally mounted to the top of the front shoe supporting arm 24 through a pivot pin 39. Moreover, the pivoted end of the main lever 38 is provided with a downwardly extending elongated portion forming a short arm 38b so that there is defined an L-shaped member with the short arm 38h and a main lever portion defining the long arm of the L and consisting of a pair of spaced parallel legs 38C, best illustrated in FIG. 3. Moreover, to interrelate the two shoe supporting arms 24 and 26, there is provided a tie bar 40 which has one end thereof pivotally connected to the short arm 38b of the main lever 38 by a pivot pin 42. The end of the tie bar 40 remote from the pivot pin 42 is threaded so as to accommodate a suitable nut 44 and slidably extends through an aperture in the rear brake supporting arm 26 thereby to adjust the maximum separation between the ends of the shoe supporting arms 24 and 26. It will be apparent that pivotal movement of the main lever 38 in a clockwise direction, as viewed in FIG. 1 of the drawings, will by virtue of the tie bar 40 cause the shoe supporting arms 24 and 26 to be moved toward each other and, hence, to apply the brake by causing the brake shoes 18 and 2t) to move toward each other and toward the brake drum 14.

In order to provide the setting force for setting the spring-set industrial brake illustrated in FIG. l, there is provided a self-contained tension spring unit generally designated by the reference numeral 46 and effective to bias the lever 38 in a clockwise direction about the pivot pin 39 with the result that the brake is applied to the brake drum 14.

To automatically release the brake 10, the electromagnetic solenoid 12 is mounted on the base 28 so that when actuated or energized it will push the lever 38 counterclockwise about the pivot pin 39 as viewed in FIG. 1 of the drawings against the force of the spring unit 46 to the position illustrated in phantom. As more clearly illustrated in FIGS. 2 and 3, the solenoid 12 is of the laminated type and provided with a frame or jacket 64 formed of a stack of laminations individually referred to as 64u, 64b, 64C, etc. of soft iron or other magnetic material and carrying a bobbin 65 having an electromagnetic winding 66. The winding 66 is provided with a pair of leads 68 and 70 for connection to a source of alternating current. The frame 64 and bobbin 65 are provided with aligned openings 72, 74, and 76 together forming a core or path 77 for magnetic flux and adapted to receive a plunger assembly 7S therein. The plunger assembly 73 includes a first or operating portion formed of a stack Si) of laminations Stia, h, Stic, etc. of magnetically attractive material. The stack S0 of laminations is positioned for movement in the core 77 between a first or deenergized position as illustrated in FIG. 2 to a second or energized position as illustrated in FIG. 3 in response to the energization of the winding 66, the stack 80 of laminations being positioned at least partially in the core or path 77 of magnetic flux in the openings 72, 74, and 76 when the plunger assembly 7S is in the cie-energized position o f FIG. 2 and the stack of laminations Si) being mutually attracted with the frame 64 for movement in the core 77 when the winding 66 is energized.

According to the present invention, the plunger assembly 78 includes a pair of pusher bars 82 providing a push type solenoid. The pusher bars S2 each includes a plunger portion 52a formed of magnetically attractive material such as soft iron and a pusher portion 32h formed of nonmagnetically attractive material such as stainless steel and secured to the plunger portion 82a in any conventional manner such as by the weld 84. A plurality of rivets 36 secure the stack of laminations 80 and the pusher bars 32 in a unitary structure to form the plunger assembly 78, the pusher bars 82 being secured to the stack of laminations 80 through the plunger portion 82a so that the plunger portion 22a of magnetically attractive mterial cooperates therewith to form a magnetic circuit portion of the plunger assembly identified by the bracketed distance m in FIGS. 2 and 3. The effective cross-sectional area of the magnetic circuit portion m is a maximum for the size of the c ore 77 and is substantially the same as would be available if the solenoid 12 were of the pull type and the pusher bar 32 were not used.

In order to connect the solenoid 12 with the load, the pusher bars S2 are pivotally connected to the main lever 33 by a bolt 88. Moreover, the end of the plunger assembly 73 which extends below the frame 64 when the winding 66 is de-energized is provided with a clevis slot or recess 90, and a pair of apertures 92 communicate therewith to provide means for connecting a pull load when the solenoid is used as a pull type. To provide strength and rigidity to the plunger assembly 78, the outer laminations 89a and certain of the inner laminations identified as SW1 are of thicker cross-section than the remaining laminations 80h, 30e, etc.

It may be desirable to weld across the end of the plunger assembly 78 opposite from the pusher portion SZb, as indicated at 94, so that the -laminations in the stack Si) as well as the pusher bar 32 form one piece, and in order for the pusher bar 82 to shear through all the rivets 36 it would also have to break the weld 94.

In operation, when the winding 66 is de-energized, the operating portion Sti of the plunger assembly 78 extends out of the lower end of the core '77, and the pusher portion 821) of the pusher rod 82 extends through the other or upper end of the core 77. Energization of the winding 66 creates a mutual magnetic attraction between the portion 80 and the frame 64, and the plunger assembly 78 is pulled upwardly to the position of FIG. 3. The pusher portion 8211, being of nonmagnetically attractive material, will not bypass magnetic iiux from the frame 64 and plunger assembly 78. Moreover, the plunger portion 82a and the operating portion 80 form part of the magnetic circiut portion m for the plunger assembly 78 which has the maximum cross-sectional area of magnetically attractive materia-l positioned in the core 77, thereby making the most eiiicient use of the magnetic material and of the space available for the plunger.

Referring now to the embodiment of FIGS. 4 and 5, there is illustrated an improved solenoid indicated generally as 100 and connected to push a lever 101 through a pivot connection such as a bolt 102. The lever 101 may, if desired, correspond to the main lever 38 of the brake unit illustrated in FIG. l. In the embodiments of FIGS. 4 and 5, the electromagnetic solenoid 100 includes a frame 104 comprised of a stack of laminations 104a, 104]), 104 c, etc. of soft iron or other magnetic material and carrying a bobbin 105 containing a winding 106 adapted to be connected to a source of alternating current. The frame 104 and the winding 106 have aligned openings forming a core 108 for receiving a solenoid plunger assembly 110.

The plunger assembly 110 contains a single pusher bar 112 secured within an operating portion formed of a stack 114 of laminations 114:1, 114b, 114e, etc. riveted together by a plurality of rivets 116. The pusher bar 112 includes a lower or plunger portion 112a, at least a part of which is formed of magnetically attractive material and which is secured within the stack 114 of laminations and additionally includes a pusher portion 112b extending through the core 108 and beyond the frame 104 and formed of nonmagnetic material. The portion of the pusher bar 112 of nonmagnetic material and the portion of the pusher bar 112 of magnetic material are joined in any suitable manner such as by the weld 118. The magnetic material which forms in part the plunger portion 112e of the pusher bar 112 does not extend the length of the stack 114 of laminations but rather the upper end of the plunger portion 112:1 which iswithin the stack 114 of the laminations is formed of the nonmagnetic material which additionally forms the pusher portion 112b. In this manner, some of the rivets 116, idenittied as 116:1, are above the weld 118 so that the weld 118 is inside the end of the stack 114, and the rivets 116e are eliective to pick up additional load from the pusher portion 112!) without the load being transmitted through the weld 118. Moreover, the plunger 110 is provided at its other end with a recess or groove 120 having a pair of aligned openings 122 in the sides thereof which are adapted for receiving a load if it i-s desired to use the solenoid 100 as a pull solenoid.

In the embodiment of FIGS. 4 and 5, the cross-section of the magnetic material of the plunger which forms a magnetic circuit portion is substantially a maximum and is substantially uniform; and, speciiically, the only portion of the magnetic circuit of the plunger 110 which has magnetic material of reduced cross-sectional area is that portion extending above the weld 118 outwardly toward the pusher portion 112b of the push bar 112 and identitied by the distance d in FIG. 5. Moreover, the non magnetic portion of the plunger portion 112e is short enough so that the small area d of reduced cross-sectional area of the magnetic circuit will not affect the force exerted by the load to any great extent.

Referring now to the embodiment of FIGS. 6 to 8, there is illustrated a solenoid wherein the nonmagnetic portion of the pusher bar extends further into the stack of laminations so that a couple of rivets may catch the inner end of the nonmagnetic bar in a manner similar to that illustrated in FIGS. 4 and 5. Referring now specially to FIGS. 6 to 8, there is fragmentarily illustrated a solenoid 130 having a plunger assembly 132 passing through a core 134 of a winding 136 and having a pair of pusher bars 138 connected to a lever 139 of an industrial brake unit which may be of the type illustrated in FIG. l. The plunger assembly 132 additionally includes the stack 140 of laminations indicated as 140g, 140b, 140C, etc. formed of magnetic material and form ing the operating portion of the plunger assembly 132. The outer laminations 140a and certain of the inner laminations 140k may be somewhat thicker than the remaining laminations in order to provide 'strength and rigidity to the stack 140. The stack 140 may be preliminarily secured together by one or more fastening means, here shown as a rivet 142. Additional rivets 144 secure the pusher bars 138 to the stack 140. In order to accomplish the advantages of the present invention, the pusher bars 138 include a pusher portion 138e formed of nonmagnetic material and extending out of the core 134 in the winding 136, and additionally includinga plunger portion 138]) formed at least in part by magnetic material, the magnetic material and the nonrnagnetic material of the pusher bar 138 being joined by a weld 146 to provide a unitary pusher bar 138. Moreover, a few of the rivets 144, identified as 144e, catch the inner end of the nonmagnetic material so that the pusher bar 13S does not have to depend entirely upon the weld 146 for its strength, but a portion of the load in the pusher bar 138 is carried by the rivets 144er. As explained above in connection with the embodiment of FIGS. 4 and 5, although the present embodiment results in a short section of the plunger assembly, identified as e in FIG. 7, which has a smaller cross-sectional area of magnetically attractive material than the remainder of the magnetic circuit in the plunger assembly 132, this section e is sufficiently short so that it does not influence the totalforce exerted by the solenoid to any great extent.

It will be seen that according to the above-described embodiments, a plunger assembly is provided for a solenoid wherein the material forming the magnetic circuit of the solenoid is of maximum cross-sectional area for the size of the opening available thereby resulting in a solenoid of maximum load capacity and providing for an equal capacity of the solenoid when adapted to either the push or the pull applications of the solenoids. Moreover, as the portion of the push bars which extend beyond the core of the solenoid are formed of nonmagnetic material, they do not bypass flux from the magnetic circuit.

While particular embodiments of the invention have been shown and described, it will be understood that various modifications will occur to those skilled in the art, and it is, therefore, contemplated by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. An electromagnetic solenoid comprising a frame of magnetic material, an electric Winding carried by said frame, said frame and said winding having aligned openings forming a core, a plunger assembly positioned in said core for movement between an energized position and a de-energized position relative to said frame in response to energization of said winding, said plunger assembly including a substantially solid stack of laminations of magnetic material and at least one pusher bar having a plunger portion secured to said laminations, at least a substantial part of said plunger portion being formed of magnetic material, said pusher bar including a pusher portion of nonmagnetfic material extending beyond said stack of laminations, said plunger assembly in its de-energized position being positioned relative to said core with said pusher portion extending through said core.

2. An electromagnetic solenoid comprising a frame of magnetic material, an electric Winding carried by said frame, said frame and said winding having aligned openings forming a path for magnetic flux, and a plunger assembly at least partially in said path for movement between an energized position and a de-energized position relative to said frame in response to energization of said plunger assembly including a substantially solid stack of laminations of magnetic material at least partially in the path `of magnetic ux when said plunger assembly is in a deenergized position and mutually attracted with said frame for movement in said path when said Winding is energized, said plunger assembly including at least one pusher bar having a plunger portion stacked with and secured to said laminations, at least a substantial part of said plunger portion being formed of magnetic material, said pusher bar including a pusher portion of nonmagnetic material extending beyond said stack of laminations through said magnetic path when said plunger assembly is in a deenergized position.

3. An electromagnetic solenoid comprising a Winding and a plunger assembly inductively associated with said Winding, said plunger assembly including a substantially solid first portion formed of magnetic material and positioned to be magnetically attracted by said Winding when said Winding is energized and at least one pusher bar having a plunger portion secured to said rst portion at least a substantial part of said plunger portion being formed of magnetic material, and said pusher bar additionally having a pusher portion extending beyond said first portion and formed of nonmagnetic material.

4. An electromagnetic solenoid comprising a frame of soft iron, an electric Winding in inductive relation with said frame, and plunger means for movement between a de-energized position and an energized position relative to said frame, said plunger means including a substantially solid stack of laminations of magnetic material adapted to be magnetically attracted by magnetic ux from said frame when said Winding is energized, and at least one pusher bar having a plunger portion stacked with and secured to said stack of laminations formed at least n substantial part of magnetic material and having a pusher portion formed of nonmagnetic material and extending beyond said stack of laminations and away from said frame when said plunger is in an energized position.

5. An alternating current solenoid comprising a Winding, means for connecting said Winding to a source of 8 alternating current, and a plunger assembly inductively associated with said winding, said plunger assembly including a substantially solid stack of laminations of magnetic material adapted to lbe magnetically attracted by said Winding when said Winding is energized by said source of alternating current and at least one pusher bar having a plunger portion stacked with and secured to said stack of laminations and having a pusher portion extending beyond said stack of laminations formed of nonmagnetic material, at least a substantial part of said plunger portion eing formed of magnetic material.

6. A solenoid for operating an industrial brake of the type including a brake drum, brake means for frictionally enga-ging said drum, lever means for actuating said brake means and movable between a brake-set position and a brake-released position, spring means biasing said lever toward one of said positions and a solenoid connected to push said lever to the other of said positions when said solenoid is energized, said solenoid comprising a winding having a core, and a plunger assembly positioned for movement in said core, said plunger assembly including a substantially solid stack of laminations of magnetic material adapted to be attracted into said core when said Winding is energized and at least one pusher bar having a plunger portion stacked with and secured to said stack of laminations, at least a substantial part of said plunger portion being formed of magnetic material, and having a pusher portion extending from said stack of laminations beyond said core and engaging said lever, said pusher portion being formed of nonmagnetic material.

References Cited in the tile of this patent UNITED STATES PATENTS 1,462,129 Thurston July 17, 1923 2,305,415 Goff Dec. 15, 1942 2,321,569 Winkler June 15, 1943 2,877,390 Trombetta Mar. 10, 1959 

1. AN ELECTROMAGNETIC SOLENOID COMPRISING A FRAME OF MAGNETIC MATERIAL, AN ELECTRIC WINDING CARRIED BY SAID FRAME, SAID FRAME AND SAID WINDING HAVING ALIGNED OPENINGS FORMING A CORE, A PLUNGER ASSEMBLY POSITIONED IN SAID CORE FOR MOVEMENT BETWEEN AN ENERGIZED POSITION AND A DE-ENERGIZED POSITION RELATIVE TO SAID FRAME IN RESPONSE TO ENERGIZATION OF SAID WINDING, SAID PLUNGER ASSEMBLY INCLUDING A SUBSTANTIALLY SOLID STACK OF LAMINATIONS OF MAGNETIC MATERIAL AND AT LEAST ONE PUSHER BAR HAVING A PLUNGER PORTION SECURED TO SAID LAMINATIONS, AT LEAST A SUBSTANTIAL PART OF SAID PLUNGER PORTION BEING FORMED OF MAGNETIC MATERIAL, SAID PUSHER BAR INCLUDING A PUSHER PORTION OF NONMAGNETIC MATERIAL EXTENDING BEYOND SAID STACK OF LAMINATIONS, SAID PLUNGER ASSEMBLY IN ITS DE-ENERGIZED POSITION BEING POSITIONED RELATIVE TO SAID CORE WITH SAID PUSHER PORTION EXTENDING THROUGH SAID CORE. 